Sigma 17-50 f/2.8 does a mud run

A friend asked me to take some pictures of a mud run. I anticipated using my 70-300VR as my primary lens but due to shooting distances and ambient light I wound up using the 17-50 more. I wasn't sure what to suspect as I haven't tried the Sigma with fast moving action before, and came away moderately impressed. I had my doubts about it's ability to consistently nail focus, but in this out I was holding the equipment back rather than vice-versa. These are mildly touched up jpegs, I normally shoot raw but with up to 10 people crossing the creek at a time I maxed out the buffer even shooting jpeg.